The present invention relates to an exposure control device for a still video camera containing an imaging device such as a CCD sensor capable of shutter control.
In a still video camera provided with so-called CCD shutter control, concerning emission timing of a flash light and accumulating time of signal charges to the CCD sensor, as disclosed in European Patent Application Publication No. 280511, for instance, emission timing of a flash light is previously determined corresponding to brightness of an object and flash light is fully emitted at a predetermined timing after starting to accumulate the signal charges. When proper exposure is attained, the accumulation of the signal charges is terminated and the signal charges are transferred to a transfer section of the CCD sensor.
Also as described in U.S. Pat. No. 4,635,123, a flash light is emitted at a given moment after starting to accumulate the signal charges and when proper exposure is attained, the flash lighting is forcedly stopped, then accumulation of the signal charges is terminated and the signal charges are transferred to the transfer section.
However, the former induces smear due to the accumulation of unnecessary charges occurring while the electronic flash remains emitting after transferring the signal charges to the transfer section, which causes deterioration in image quality.
Also in the latter case, due to unnecessary charges in the transfer section are not removed immediately before transferring the signal charges to the transfer section, it is not well to remove smear caused by flash light.
In such a known manner that the accumulated charges are transferred to a vertical transfer section during the flash lighting or in response to the timing of forcedly stopping the emission of flash light, unnecessary charges in the vertical transfer section are mixed up with the signal charges to produce smear and lower the image quality.
Although, the devices described in the above prior art need to have a sequence of flash lighting at a given moment after starting to accumulate the signal charge for attaining a picture in which both the available light and the flash light properly contribute, it is expected to provide a device in which both the available light and the flash light can contribute to get a proper exposure even if the flash light is emitted at the instant of the starting to accumulate the signal charges.
Furthermore, the prior art fails to control the flash light by using a distance information for exposure control by CCD shutter function, disregarding that the affecting amount of flash light for exposure varys corresponding to an object distance.